Use array typehints for array arguments

[stof]

Assertions are not blocking the invalid input by default (they might get disabled entirely or be configured to trigger only a warning). Using an array typehint is better to enforce the contract.

Remaining assertions are about scalar types, which cannot go to the method signature until the min PHP requirements is bumped to PHP 7.0.

[stof]

On a side note, the new major release might bump the min requirement to something newer than PHP 5.4. 5.4 is EOLed since quite some time: https://secure.php.net/supported-versions.php

[pitbulk]

Hi,

I aligned the php min version requirements with the xmlseclibs library.

There was a debate there about what min PHP version put on composer.

[pitbulk]

btw, Thanks for your contributions ;)

[mlocati]

Totally off-topic, but this PR reminds me a recent article I wrote about type hinting: it may be useful for others too.

[stof]

@pitbulk the fact that xmlseclibs supports 5.4+ only means you cannot support 5.3. It does not mean you need to align on it on both sides.

[stof]

and I agree that bumping requirement just for the sake of it is not that useful. Here, I was suggesting to bump it to be able to use scalar typehints (so having a benefit for the library)

[pitbulk]

but the truth is that there are php-saml uses on PHP apps 5.4 and 5.5 and the idea of the 3.0.0 branch is to use it for PHP5 & PHP7 , so old php-saml 2.X branch can be declared deprecated (so I don't need to maintain 2 different branches. I do it for python-saml and python3-saml and similar can apply for Java, Ruby..).